Aircraft main engines not only provide propulsion for the aircraft, but in many instances may also be used to drive various other rotating components such as, for example, generators, compressors, and pumps, to thereby supply electrical, pneumatic, and/or hydraulic power. Generally, a gas turbine engine includes a combustor, a power turbine, and a compressor. During operation of the engine, the compressor draws in ambient air, compresses it, and supplies compressed air to the combustor. The compressor also typically includes a diffuser that diffuses the compressed air before it is supplied to the combustor. The combustor receives fuel from a fuel source and the compressed air from the compressor, and supplies high energy compressed air to the power turbine, causing it to rotate. The power turbine includes a shaft that may be used to drive the compressor.
Gas turbine engines generally take the form of an axial compressor or a centrifugal compressor, or some combination of both (i.e., an axial-centrifugal compressor). In an axial compressor, the flow of air through the compressor is at least substantially parallel to the axis of rotation. In a centrifugal compressor, the flow of air through the compressor is turned at least substantially perpendicular to the axis of rotation. An axial-centrifugal compressor includes an axial section (in which the flow of air through the compressor is at least substantially parallel to the axis of rotation) and a centrifugal section (in which the flow of air through the compressor is turned at least substantially perpendicular to the axis of rotation).
As mentioned above, compressors often include a diffuser to reduce the velocity of the air traveling from the compressor to the combustor, for example in a gas turbine engine with a through flow combustor. In addition, certain compressors (e.g., certain centrifugal compressors) have both a first diffuser located relatively early in the compressor flow passage away from the combustor and a second diffuser (often called a pre-diffuser) located later in the flow passage proximate the combustor. However, to date, it has been difficult to implement such additional diffusers, or pre-diffusers, in connection with compressors for gas turbine engines, for example those with axial compressors and/or in-line combustors. For example, such pre-diffusers have generally been significantly large. As a result, any placement of such a pre-diffuser in a centrifugal compressor could generally result in an undesirable increase in the length and/or weight of the engine. In addition, control of air flow through such pre-diffusers can also be difficult.
Accordingly, there is a need for an improved diffuser system for a compressor, such as a centrifugal compressor, for example without significantly increasing size and/or weight and/or with improved diffusion and/or control of air therein. There is also a need for a compressor, such as a centrifugal compressor, with an improved diffuser system, for example without significantly increasing size and/or weight and/or with improved diffusion and/or control of air therein. There is a further need for a gas turbine engine with a compressor, such as a centrifugal compressor, with an improved diffuser system, for example without significantly increasing size and/or weight and/or with improved diffusion and/or control of air therein. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.